If you have hard water aggravated by iron, you understand how difficult iron is to deal with. Rid O' Rust formula 3000 is designed for the most extreme conditions with water hardness over 15 grains per gallon and pH less than 6.0. For those who don't understand the technical jargon, that's really bad water. Formula 3000 can handle it! If you've tried other products and been disappointed, it's time to try the best and be Rid O' Rust once and for all! The American Hydro Systems Rid O' Rust Formula 3000 Rust Stain Preventer is designed for hard water and acidic conditions. One gallon treats up to 125,000 gallons of water. Our most potent formula.